Mechanical interlock for electric switches



April 16, 1946. s. L MQFARLAND, JR

MECHANICAL INTERLOCK FOR ELECTRIC; SWITCHES Filed Aug. 12, 1944 F .n W hGeofge L. McFarlancLJfi,

' Patented Apr. 16, 1946- MECHANICAL New York INTERLOCK FOR ELECTRICswrrcnns George L. McFarland, Jr., Scotla, N. Y., assignor to GeneralElectric Company,

a corporation of Application August 12, 1944, Serial No. 549,253

3 Claims.

My' invention relates to mechanical interlocks for electric switches,more particularly to a mechanical interlock between twoelectromagnetically operated reversing switches in the circuit of anelectric motor for preventing one contactor from picking up until theopposite contactor has dropped out almost completely, and has for itsobject a simple, reliable and inexpensive interlock providing for aconvenient adjustment of the interlocking members and for opening biason the contactor which is'being opened.

For the forward and reverse operation of an lectric motor, twocontactors are provided, which contactors are selectively closed to givethe desired direction of rotation of the motor. A characteristic of suchforward and reverse contactors is that the closure of both at the sametime forms a short circuit across the supply line for the motor. Toguard against this false operation, various mechanical interlocks havebeen provided between the two contactors, which interlocks require theopening of one contactor before the other can be closed.

Ordinarily the closure of both contactors at the same time results frommanual interference with their operation or because of the welding ofthe contacts of one contactor so that it cannot drop.

out.

The simplest interlock is a pivoted bar having its ends connected to thetwo contactors so that one contactor picks up at the same rate as theother drops out. This, however, does not provide suflicient clearanceinsome cases between the contacts of the opening contactor at the timeth other closes to take care of short circuits caused by arcing betweenthe opening contacts. Other interlocks provide for full interference,that is,

prevent any movement of the reversin contactor less than ninety degreesso that when the open contactor is energized, an opening force isapplied to the closed contactor.

For a more complete understanding of my invention, reference should behad to the accompanying drawing, Fig. l of which is a fragmentaryelevation view of two contactors provided with mechanical interlockmeans embodying my invention; Fig. 2 is a view similar to Fig. l butshowing one of the contactors in its closed circuit position; Fig. 3 isa sectional view taken along the line 3-4 of Fig. 1 looking in thedirection of the arrows; while Fig. 4 is a sectional view along the line4-4 of Fig. 1 looking in the direction of the arrows.

Referring to the drawing, I have shown my invention in one form asapplied to two contactors having stationary operating coils i and 2which, when energized respectively, pick up rectilinear- 1y movablearmatures 3 and I. These armatures are each connected to suitableelectric switching means (not shown) such as described and claimed inPatent 2,064,632, issued to Richard H. Schmitt, on December 15, 1936.The two contactors are secured to a common support, such as metal panel5, in spaced relation with each other and in upright positions so thattheir armatures 3 and I move in parallel paths.

Th interlock means between the two contactors comprises two levers 6 andI mounted on piv ots 8 and 9 between the two contactors. As

shown, the levers are made of a suitable metal, such as steel, althoughthey may be made of a suitable molded plastic material. The outer endsof these levers, shown as rods, extend loosely through loops on thelower ends of two straps l0 until the other contactor has droppedcompletely open. Such interlocks, however, are expensive to manfactureand require fine adjustments.

In accordance with my invention, I provide a mechanical interlock whichis a compromise between the two interlocks referred to aboveand permitsthe reverse contactor to pick up very slowly until the forward contactorhas nearly reached its full open position. In one form of my invention,I provide two levers which are mounted on adjustable pivots between thetwo contactors and have their outer ends secured to the two contactors.The inner adjacent ends of these two levers are arranged to interferewith each other to give the desired interlocking, and are furthermorearranged when one contactor is closed to extend at an angle with eachother of and II having their upper ends secured respectively to thearmatures 3 and 4. Thus, each of the levers 6 and l is movable on itspivot in response to upward and downward movement of the armature towhich it is secured.

The inner ends of the levers consist of flat bars or straps I 2 and I 3which are bent upward, as seen in Figs. 1 and 2, with respect to theouter ends of the levers from points opposite th pivots '8 and 9. Thesetwo ends are adjusted so as to be in closely spaced relation with eachother, as indicated in Fig. 1, when the armatures are both in theirlowermost unattracted positions. When one armature is moved upward byits coll, the inner end of its lever moves inthe path of the other leverand thereby prevents the other armature from moving upward at the sametime. As shown in Fig. 2, the armature 3 is in'its upperattracted'position and the inner end I! has moved directly in the pathof the inner end l3 of the other lever. Preferably, the adjustment issuch that the inner end of each lever in its picked up position isspaced somewhat from the other lever, as indicated in Fig. 2. It willthus be observed that the armature 4 can be moved upward only a verysmall amount as long as the inner end of the lever 8 is directly in itspath, but when the armature 3 has moved downward nearly to itsunattracted or fully open position, the lever 8 moves out of the path ofthe lever 1, which then canmove downward for movement of the armature lupward to its fully attracted position.

Another feature of my invention is the construction and arrangement ofthe inner ends l2 and I'3 so that when one of the armatures is in itspicked up position, these inner ends are at an angle with each otherwhich is less than ninety degrees, whereby a positive opening force isapplied to the opening contactor. Preferably, this angle isapproximately seventy-five degrees. As shown in Fig. 2, this angularrelation provides for the application of an appreciable opening force tothe inner end l2 by the inner end IS in the event that the coil 2 isenergized with the armature 3 picked up. In other words, a component ofthe force applied by the inner end Hi to the inner end I2 is in adirection laterally with respect to the inner end I! and in acounterclockwise direction so as to pull the armature 3 downward. Thistakes care of the opening of either contactor, in the event that itscontacts have welded, when the other contactor is energized, the coil ofthe first closed contactor of course being at that time deenergized. Tofacilitate this opening action, graphite grease is applied to theengaging surfaces of the inner ends, and the edge of each which engagesthe other is rounded somewhat.

To provide for accurate adjustment of the pivots 8 and 9 with respect toeach other, I secure the pivots on plate members l4 and I5 which areclam ed in place against the front surface of the panel 5 by means of aclamping plate l6 and two pairs of screws [1 and I8 extendingrespectively through slots i9 and 20 in the members H and 15. Alsosecured to the clamping plate It at its middle is a cam member 2 I, thecam member having a round projection 22 which has a screw slot 23 at thefront of the plate. Thus, by loosening the screws [1 and 18, thesupports M and I5 may be adjusted accurately apart by suitably turningthe cam 2|, thereby suitably to adjust the interference between the ends[2 and I3, after which the screws are tightened.

While I have shown a particular embodiment of my invention, it will beunderstood, of course, that I do not wish to be limited thereto sincemany modifications may be made, and I there fore contemplate by theappended claims to cover any such modifications as fall within the truespirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent 0f the UnitedStates is:

1. In combination, a support, a pair or electric switches mounted inspaced relation on said support and adapted for independent operation tocircuit controlling positions, a pair of supporting members mounted onsaid support in spaced relation with each other, a lever pivotallymounted on each of said members, a mechanical connection between each ofsaid switches and one of said levers, the inner adjacent ends of saidlevers being shaped and arranged to interfere with each other when one01 said switches is closed so as to prevent the closure of the other ofsaid switches, and cam means mounted between said supporting members andmovable to engage and adjust said supporting members with respect toeach other thereby to adjust the interfering relation between theadjacent ends of said levers.

2. In combination, a support, a pair of electromagnetically operatedelectric switches mounted on said support in spaced relation and adaptedfor independent operation to circuit controlling positions, a pair ofsupporting members mounted on said support in spaced relation with eachother, a lever pivotally mounted on each or said supporting members, amechanical connection between each of said switches and the outside armof each of said levers, the inner adjacent arms of said levers beingshaped and arranged to interfere with each other when one of saidswitches is closed so as to prevent the closure of the other of saidswitches and to extend at an angle, of less than ninety degrees withrespect to each other when one of said switches is closed so thatattempted closure of the open switch applies an opening force to theclosed lever and switch, and a cam mounted on said support between saidsupporting members, said cam being movable to engage and adjust saidsupporting members with respect to each other thereby to adjust theinterferin relation between the adjacent ends of said levers.

3. In combination, a support, a pair of electric switches mounted onsaid support in spaced relation and adapted'for independent operation tocircuit controlling positions, a pair of supportin members mounted onsaid support in spaced relation with each other, a lever pivotallymounted on each of said supporting members, a connection between each ofsaid switches and one of said levers, the inner adjacent ends of saidlevers being shaped and arranged to interfere with each other when oneof said switches is closed so as to prevent the closure of the other ofsaid switches and to extend at an angle of less than ninety de' greeswith respect to each other when one of said switches is closed so thatattempted closure of the other switch applies an opening force to theclosed lever and switch, and a cam rotatabiy mounted between saidsupporting members and rotatable to move said supporting members withrespect to each other thereby to adjust the interfering relation betweenthe adjacent ends of said levers.

GEORGE L. MCFARLAND, JR.

